PLAB 1 Pharmacology and Therapeutics 2

Question 1

A patient is prescribed amoxicillin for a chest infection. They mention they are also taking the combined oral contraceptive pill. According to current BNF guidance, does amoxicillin interact with the combined oral contraceptive?

Accepted Answer

No — non-enzyme-inducing antibiotics like amoxicillin do not reduce the efficacy of the combined oral contraceptive according to current evidence and BNF guidance

Answer

Current BNF and FSRH guidance states that non-enzyme-inducing antibiotics (including amoxicillin) do not reduce the efficacy of the combined oral contraceptive. Only enzyme-inducing drugs (e.g., rifampicin, carbamazepine, phenytoin) require additional contraceptive precautions.

Question 2

A patient with chronic kidney disease stage 4 is found to have a potassium level of 6.8 mmol/L. ECG shows peaked T waves. What is the most important immediate treatment?

Accepted Answer

IV calcium gluconate 10% to stabilise the myocardium, followed by insulin-dextrose infusion to reduce serum potassium

Answer

Severe hyperkalaemia (>6.5 mmol/L) with ECG changes is a medical emergency. IV calcium gluconate is given first to stabilise the myocardium (does not reduce potassium). Insulin-dextrose drives potassium intracellularly. Nebulised salbutamol can also help. Calcium Resonium removes potassium but acts too slowly for acute management.

Question 3

According to NICE guidelines, what is the first-line antihypertensive for a 60-year-old Caucasian patient with no comorbidities?

Accepted Answer

Calcium channel blocker (e.g., amlodipine)

Answer

NICE hypertension guidelines (NG136) recommend a calcium channel blocker (CCB) as first-line for patients aged ≥55 or of African/Caribbean descent. ACE inhibitors/ARBs are first-line for patients aged <55 (non-African/Caribbean). At age 60 without comorbidities, amlodipine would be appropriate.

Question 4

A patient taking co-amoxiclav develops profuse watery diarrhoea with abdominal pain 5 days into the course. Stool sample tests positive for Clostridioides difficile toxin. What is the first-line treatment?

Accepted Answer

Stop the causative antibiotic and start oral vancomycin

Answer

Current UK guidelines recommend oral vancomycin as first-line treatment for C. difficile infection (replacing metronidazole, which is now second-line). The causative antibiotic should be stopped if possible. Loperamide is contraindicated as it can lead to toxic megacolon.

Question 5

A patient on long-term prednisolone 20 mg daily for rheumatoid arthritis wants to stop the medication. What is the correct approach?

Accepted Answer

Gradual dose reduction is essential to avoid adrenal crisis, as long-term corticosteroids suppress the hypothalamic-pituitary-adrenal (HPA) axis

Answer

Long-term corticosteroid use (>3 weeks) suppresses the HPA axis. Abrupt withdrawal can cause adrenal crisis (hypotension, shock, death). The BNF recommends gradual dose tapering, typically reducing by 1-2.5 mg every 2-4 weeks, with monitoring for symptoms of adrenal insufficiency.

PLAB 1 Practice Test

PLAB 1 Practice Test

PLAB 1 Pharmacology and Therapeutics 2